R1003.18

Section R1003.18 is titled 'Chimney clearance' and covers requirements for masonry chimneys. The requirement for maintaining clear air space (except where allowed for fireblocking) between a chimney and combustible materials, dependent on the location of the chimney is established. The purpose of this section is to prevent the building from catching fire. This section has 3 exceptions which allow for no clear air space where systems have been tested or designed to prevent combustible materials from catching fire. The purpose of these exceptions is to allow for practical arrangements where there is low risk of starting the building on fire.

The model shows a section of an interior chimney and fireplace with combustible framing being installed around the chimney and a 2" air space highlighted between the chimney and the framing.